Several European countries have faced unusually frequent outbreaks of histamine poisoning from fish over the past few months.

Croatia, Denmark, France, Italy, Poland and Spain have all reported outbreaks this season. More than 100 people in Spain alone had been sickened by May of this year. Other countries reported abnormal clusters of human cases of histamine poisoning, also known as scombroid poisoning.

The suspected culprit is chilled yellow fin tuna from Spain, based on reports from several of the countries involved. Products suspected to be unsafe to eat have been recalled.

To get histamine poisoning — which makes up about 40% of all seafood-related foodborne illness cases — you have to eat spoiled fish. It used to be thought that only fish from the Scombridae family could cause the sickness, but it’s now understood that many fish can contain histamine, including tuna, mahi-mahi, marlin, bluefish, sardines, anchovy, bonito, herring and mackerel.

Like most foodborne illnesses, histamine poisoning symptoms are unpleasant, to say the least. They include rashes, nausea, vomiting, diarrhea, hypotension, heart palpitations and muscle weakness. Symptoms can show up fast — sometimes just 10 minutes or so after eating. In the absolute worst cases, paralysis and death have been reported. Fortunately, most cases are manageable.

How it works

Very few people intentionally chow down on spoiled or rotting fish — in most cases, it’s accidental, as the fish was not kept cold enough. Histamine that forms on decaying fish cannot be destroyed by cooking or freezing, so unfortunately both your raw sushi and your seared mahi-mahi can make you sick. You also can’t see or smell histamine.

“The histamine that makes you sick is formed when tuna is not properly refrigerated after it’s caught. During that time, unless the fish is kept cold, bacteria (especially Klebsiella pneumoniae) go to work. At temperatures between 75°F and 90°F the bacteriaflourish, and the [bacteria] carry out a biochemical reaction catalyzed by a bacterial enzyme called histidine decarboxylase. The enzyme converts the amino acid histidine to histamine. Once formed, histamine is stable to heat.”